System and method used in a gas turbine engine for minimizing nitrogen oxide emission

ABSTRACT

A system and method used in a gas turbine engine for minimizing nitrogen oxide content in the exhaust gases of the gas turbine engine. According to the method having the step of feeding partially contaminated air at least into primary air intakes of the combustor of the gas turbine engine, the system comprises a preliminary combustor for putting the step into practice. The preliminary combustor includes primary air intakes communicating with the air compressor of the gas turbine engine for receiving primary air therefrom, additional air intakes communicating with the air compressor for receiving therefrom additional air as a diluent, a fuel injector communicating with the fuel pump of the gas turbine engine for receiving a liquid fuel therefrom, and an outlet connected to the combustor or the air compressor upstream thereof for introducing the diluted burned gases into the combustor of the gas turbine engine as primary air therefor. Thus, the maximum temperature in the combustion zone of the gas turbine engine is effectively reduced with a resultant reduction in the nitrogen oxide emission. The system may be provided with a heat exchanger interposed between the outlet of the preliminary combustor and the primary air intakes of the gas turbine engine for improving reduction efficiency of the nitrogen oxide emission.

United States Patent Handa Feb. 19, 1974 SYSTEM AND'METIIoo USED IN A GAS I TURBlNE ENGINE FOR MINIMIZING NITROGEN OXIDE EMIssIoN [75] Inventor: Noritoshi Handa, Yokohama, Japan [73] Assignee: Nissan Motor Company, Limited,

Yokohama, Japan [22] Filed: Dec. 1, 1971 [21] Appl. No.: 203,546

[30] Foreign Application Priority Data Dec. 22, 1970 Japan 45/129344 [52] US. Cl 60/39.02, 60/39.52, 60/39.65 [51] Int. Cl F02c 3/04, F020 7/14 [58] Field of Search 60/39.52, 39.65, 39.69, 261,

[5 6] References Cited UNITED STATES PATENTS 3,541,790 11/1970 Kellet 60/39.65 X 2,901,032 8/1959 Brola 60/39.74 R 2,721,444 10/1955 Johnson. 60/261 3,656,298 4/1972 Wade 60/39.52 X 3,048,014 8/1962 Schmidt.... 60/39.72 R X 3,705,492 12/1972 Vickers 60/39.65 X 2,773,350 12/1956 Barrett et al..... 60/39.72 R X 2,913,874 11/1959 Travers 60/39.72 R

Primary ExaminerCarlton R. Croyle Assistant Examiner-Robert E. Garrett [57] ABSTRACT A system and method used in a gas turbine engine for minimizing nitrogen oxide content in the exhaust gases of the gas turbine engine. According to the method having the step of feeding partially contaminated air at least into primary air intakes of the combustor of the gas turbine engine, the system comprises a preliminary combustor for putting the step into practice. The preliminary combustor includes primary air intakes com municating with the air compressor of the gas turbine engine for receiving primary air therefrom, additional air intakes communicating with the air compressor for receiving therefrom additional air as a diluent, a fuel injector communicating with the fuel pump of the gas turbine engine for receiving a liquid fuel therefrom, and an outlet connected to the combustor or the air compressor upstream thereof for introducing the diluted burned gases into the combustor of the gas turbine engine as primary air therefor. Thus, the maximum temperature in the combustion zone of the gas turbine engine is effectively reduced with a resultant reduction in the nitrogen oxide emission. The system may be provided with a heat exchanger interposed between the outlet of the preliminary combustor and the primary air intakes of the gas turbine engine for improving reduction efficiency of the nitrogen oxide emission.

9 Claims, 5 Drawing Figures SYSTEM AND METHOD USED IN A GAS TURBINE ENGINE FOR MINIMIZING NITROGEN OXIDE EMISSION The present invention relates to a gas turbine engine and, more particularly, to a system used in a gas turbine engine for minimizing nitrogen oxide content in the exhaust gases thereof.

Regarding exhaust emission, as is well known, a gas turbine engine is advantageous in that, since it can maintain a continuous combustion with a sufficient amount of additional diluent air existing, reaction intermediates such as carbon monoxide or hydrocarbons are reduced to a minimum level. However, reaction itself takes place in an intensively stirred condition in an environment of abundant oxidizer, so that nitrogen oxide content in the exhaust gases sometimes assumes a considerable value.

In order to minimize the nitrogen oxide emission, the present invention contemplates to calm down the intensity of the reaction experienced in the combustion chamber of the gas turbine engine. For this purpose, air which contains more inert' composition than ambient fresh air is fed at least into primary air intakes of the combustion chamber. This is based on my experiment, in which the air used has been partially contaminated with burned gases before it is introduced into the combustion chamber. In order to obtain the contaminated air or air-diluted combustion gases, a preliminary combustor is provided, which may communicate either with the primary air intakes of the gas turbine engine or with the upstream of the air compressor of the gas turbine engine. Thus, the contaminated air is used as a primary air in the former case, while it is distributed not only to the primary air intakes but to the additional (secondary and/or tertiary) air intakes, in the latter case. In both cases, if desired, a heat exchanger may be provided for cooling the contaminated air through heat transfer.

The reason why such introduction of. the contaminated air into the combustion chamber is remarkably effective in minimizing nitrogen oxide emission is not still absolutely clarified, but one of determinative candidates for the reason is the substantial reduction in the maximum temperature in the combustion zone. This reduction is suspected to lead in turn to reduction in possibility of dissociation ofbumed gases, which is believed as a major factor for producing nitrogen oxides. Another candidate is reduction in possibility of recombination of dissociated nitrogen molecules, if any, with active dissociated oxygen molecules. This is conceivable because there exists an increased amount of burned inert gases in the combustion zone.

In the drawings:

FIG. 1 is a flow chart illustrating the basic concept of the present invention;

FIG. 2 is a flow chart illustrating one embodiment of the invention;

FIG. 3 is a sectional view showing a nitrogen oxide content minimizing system diagrammatically shown in FIG. 2;

FIG. 4 is similar to FIG. 2 but shows another slightly modified embodiment of FIG. 2; and

FIG. 5 is similar to FIG. 2 but shows a further embodiment of the invention.

Referring now to FIG. 1, a common gas turbine engine as generally designated at numeral is provided with a combustor which includes a combustion chamber 11, a swirler 12 and a fuel injector 13. The fuel injector 13 has fluid communication with a fuel pump 14 for receiving a liquid fuel therefrom. A turbine 15 is also provided in the gas turbine engine 10 for extracting an output power from the energy contained in the combustion products of the combustion chamber 11. Compressed air is supplied to the combustion chamber 11 by an air compressor 16 as secondary and tertiary air, as shown.

According to an inventive concept of the present invention, partially contaminated air is supplied as primary air to the combustion chamber 11 through the swirler 12. The contaminated air can be produced in any suitable fashion, but a practical advantage is obtained if it is composed of burned gases, as has been discussed.

More detailed explanation will be made with reference to FIGS. 2 and 3, in which like numerals indicate counter-parts shown in FIG. 1. According to the invention, a system 20 is provided for minimizing nitrogen oxide content in the exhaust gases of the main combustor l l. The system 20 of the invention is provided with a preliminary combustor 21 which is mounted in an elongated annular air conduit 22 of the main combustor 1 l. The preliminary combustor 21 includes primary air intakes 23 and additional air intake 24, for example, secondary and tertiary air intakes. Ambient fresh air supplied from the air compressor 16 is distributed in accordance with predetermined openings of the air intakes 23 and 24. In this instance, a sufficient amount of the supplied air is introduced into the preliminary combustor 21 through the additional air intakes 24 so as to dilute and cool down the burned gases, which :are mainly produced by the combustion of an injected fuel with air supplied from the primary air intakes 23. A suitable liquid fuel is injected into the preliminary combustor 21 by a fuel injector 25, which is in communication with the fuel pump 14 through a fuel regulator 26. An outlet 27 of the preliminary combustor 21 is directly secured to the main combustor 11 at the upstream of the swirler 12, as shown. An ignition plug 26 may be mounted on the preliminary combustor 21 for igniting a liquid fuel supplied from the fuel injector- 25.

Thus, the preliminary combustor 21 can be considered a burned gas generator for feeding the partially contaminated air to the main combustor 11, because the burned gases are highly diluted with the additional air. In operation, therefore, the primary air containing burned gases and remaining oxygen gases is introduced into the main combustor 11 through the swirler 12. A liquid fuel pumped out by the fuel pump 14 is metered at a fuel regulator 28 and, then, is supplied to the fuel injector 13 of the main combustor 11. The liquid fuel injected by the fuel injector 13 is ignited by an ignition plug 29, which is mounted on the main combustor 11. Additional diluent air supplied through the elongated annular air conduit 22 is concurrently introduced into the main combustor 11 through secondary and tertiary air intakes 31 and 32, which are formed in the housing of the main combustor l 1. From a practical standpoint, the best result can be obtained when fuel flow rates respectively supplied to the preliminary and main combustois 21 and 11 are l 9.

When, moreover, the system 20 of the invention is employed in an automobile having a gas turbine engine, the preliminary combustor 21 is operated not only as a burned gas generator during all the driving modes but I as a power generator during idling and light load ditions. On the other hand, the main combustor 11 be operated only when the automobile is under 1 load condition. This operational characteristics uld also be appreciated in view of fuel consumption nomy.

slightly modified embodiment is shown in FIG. 4, which the flow chart is illustrated in a simplified mer. in this embodiment, the system of the intion is provided with a heat exchanger 33 in addil to the preliminary combustor 21. This heat exnger 33 is interposed between the outlet of the pre- .nary combustor 21 and the upstream of the swirler of the main combustor 11 for cooling the partially taminated air through heat transfer. urning now to FIG. 5, the burned gases produced in preliminary combustor 21 is fed back to the air ipressor 16. Thus, the contaminated air is partially ulated in the circuit including the preliminary comtor 21 and the air compressor 16, and as such is supd to the main combustor not only through the la 12 as primary air but also through the secondary tertiary air intakes 31 and 32. Therefore, the final t'uel ratio in the preliminary combustor 21 should be ted toward a richer side than the previous two ex- )les. This embodiment may also be provided with heat exchanger 33 for the same purpose as before. .esired, an auxiliary turbine 34 may be provided 'nstream of the preliminary combustor 21 and upam of the heat exchanger 33 for directly extracting tuxiliary output power from the energy contained in burned gases of the preliminary combustor 21. This ossible because the overall combustion in the prenary combustor 21 takes place at a richer side, rely, in the neighbourhood of the stoichiometric dition.

' hat is claimed is:

. in a gas turbine engine, comprising a combustor ing a swirler and a fuel injector, primary air intakes; :ast one additional air intake, an air compressor for plying air to the combustor through said additional make, a fuel pump for supplying a liquid fuel to the injector, a turbine extracting an output power from energy contained in the combustion products of the ibustor, and a preliminary combustor for feeding :liluted combustion gases to the first-named corn tor, which preliminary combustor includes:

rimary air intakes communicating with the air compressor for receiving primary air therefrom; lditional air intakes communicating with the air compressor for receiving therefrom additional air as a diluent;

a fuel injector communicating with the fuel pump for receiving a liquid fuel therefrom; and

an outlet communicating with the primary intakes of the combustor.

2. A gas turbine engine according to claim 1, wherein the outlet of the preliminary combustor communicates with the primary air intakes of the combustor through the swirler thereof.

3. A gas turbine engine according to claim 2, and further comprising a heat exchanger interposed between the outlet of the preliminary combustor and the primary air intakes of the combustor for cooling the air burned gases through heat transfer before feeding the same to the primary air intakes of the combustor.

4. A gas turbine engine according to claim 1, wherein the outlet of the preliminary combustor communicates with the primary air intakes of the combustor through the air compressor.

5. A gas turbine engine according to claim 4, and further comprising a heat exchanger interposed between the outlet of the preliminary combustor and the air compressor for cooling the air burned gases through heat transfer before feeding the same to the air compressor.

6. A method of minimizing nitrogen oxide content in the exhaust gases of a gas turbine engine by feeding airdiluted combustion gases to the primary air intakes of the combustor of a gas turbine engine comprising:

burning an injected fuel in a preliminary combustor,

diluting the burned gases with additional air in the preliminary combustor, and

introducing at least a portion of the air-diluted combustion gases into the primary air intakes.

7. Method according to claim 6, wherein said feeding step further comprises the step of cooling said diluted burned gases through a heat transfer before introducing the same into said primary air intakes.

8. Method according to claim 6, wherein said feeding step further comprises the step of:

feedling back the diluted burned gases to the primary 'air intakes of both the preliminary combustor and the combustor of the gas turbine engine.

9. Method according to claim 8, wherein said feeding step further comprises the step of cooling said diluted burned gases through a heat transfer before introducing the same into the primary air intakes of both the preliminary combustor and the combustor of the gas turbine engine. 

1. In a gas turbine engine, comprising a combustor having a swirler and a fuel injector, primary air intakes, at least one additional air intake, an air compressor for supplying air to the combustor through said additional air intake, a fuel pump for supplying a liquid fuel to the fuel injector, a turbine extracting an output power from the energy contained in the combustion products of the combustor, and a preliminary combustor for feeding air-diluted combustion gases to the first-named combustor, which preliminary combustor includes: primary air intakes communicating with the air compressor for receiving primary air therefrom; additional air intakes communicating with the air compressor for receiving therefrom additional air as a diluent; a fuel injector communicating with the fuel pump for receiving a liquid fuel therefrom; and an outlet communicating with the primary intakes of the combustor.
 2. A gas turbine engine according to claim 1, wherein the outlet of the preliminary combustor communicates with the primary air intakes of the combustor through the swirler thereof.
 3. A gas turbine engine according to claim 2, and further comprising a heat exchanger interposed between the outlet of the preliminary combustor and the primary air intakes of the combustor for cooling the air burned gAses through heat transfer before feeding the same to the primary air intakes of the combustor.
 4. A gas turbine engine according to claim 1, wherein the outlet of the preliminary combustor communicates with the primary air intakes of the combustor through the air compressor.
 5. A gas turbine engine according to claim 4, and further comprising a heat exchanger interposed between the outlet of the preliminary combustor and the air compressor for cooling the air burned gases through heat transfer before feeding the same to the air compressor.
 6. A method of minimizing nitrogen oxide content in the exhaust gases of a gas turbine engine by feeding air-diluted combustion gases to the primary air intakes of the combustor of a gas turbine engine comprising: burning an injected fuel in a preliminary combustor, diluting the burned gases with additional air in the preliminary combustor, and introducing at least a portion of the air-diluted combustion gases into the primary air intakes.
 7. Method according to claim 6, wherein said feeding step further comprises the step of cooling said diluted burned gases through a heat transfer before introducing the same into said primary air intakes.
 8. Method according to claim 6, wherein said feeding step further comprises the step of: feedling back the diluted burned gases to the primary air intakes of both the preliminary combustor and the combustor of the gas turbine engine.
 9. Method according to claim 8, wherein said feeding step further comprises the step of cooling said diluted burned gases through a heat transfer before introducing the same into the primary air intakes of both the preliminary combustor and the combustor of the gas turbine engine. 